SQN-4S IVe User's Handbook
Rechargeable nickel cadmium cells may be employed for maximum economy, but types
fitted with solder tags may be found mechanically unsuitable. If all cells are good they
may be recharged in series using an external charger unit, which can be connected to
the 4-way connector [DC] next to the battery compartment door. The endurance of
nickel cadmium cells will be about half that of alkaline cells.
For maximum life, lithium cells giving 3 volts per cell can be used, since the power
supply will accept inputs up to 24 volts. The use of ordinary ‘dry cell’ carbon zinc cells,
which may leak and cause extensive damage, is definitely not recommended. In any
case, when used in the SQN-4S they give a small fraction (about one fifth) of the life of
alkaline cells, so they are a false economy. If such cells are fitted in an emergency, it is
most important that they be removed immediately after use. Similarly, any type of
battery should be removed if the mixer is to be stored for any length of time or
transported, particularly by air.
To fit the cells, slide the battery door catch on the right side of the mixer towards the
front panel to release the door and insert two rows of four cells in series, so that the
lower tube has the positive poles facing the door and the upper tube the negative poles,
as is indicated on the door itself. If the cells are inserted with incorrect polarity the
mixer will not function; an internal protection circuit prevents damage to the mixer
power supply. When operating from the internal battery supply, switch the rotary power
selector switch, situated at the front of the connector panel, to the [BAT] position to
power the mixer. A green LED between the meters lights up to indicate that the mixer is
switched on.
The right channel meter doubles as a voltmeter for the power supply when the adjacent
[BATT] push button switch is depressed. The mixer is guaranteed to work down to a
battery voltage of 6 volts, so that as long as the battery meter reads on scale,
performance will be to specification. If the voltage is allowed to fall lower (to about 4.8
V) then eventually the internal power rails will fall. This will affect the headroom of the
output and monitor amplifiers and the setting of the Line-Up tone; ultimately the
performance of the whole mixer will be degraded. It is worth noting that as the battery
voltage falls, the current drawn by the power supply will increase to maintain the
required power input. The battery voltage is, therefore, likely to fall quite quickly as the
cells become exhausted.
2. EXTERNAL POWER SOURCE. A direct current supply in the range 6 to 24 volts can
be connected to the 4-Way connector [DC] next to the battery door. In order not to
restrict the usable types of powered microphones, the power supply must be capable of
delivering 2.5W while maintaining an output voltage in the required range.
The mixer’s power input terminals float with respect to the SQN-4S ground, so a supply
which does not share a ground with the SQN-4S may be used, e.g. a camera battery.
The power supply input of the SQN-4S is protected against connection of an external
voltage with reversed polarity. If it is desired to power the SQN-4S from an external
DC supply at higher voltage than 24V, reference should be made to the manufacturers
To power the SQN-4S from an external supply the rotary Power Selector Switch on the
front of the connector panel must be turned to the [EXT] position.
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